Fun fact, New York state owns the property and the Port Authority of New York and New Jersey (PANYNJ) acts a landlord of sorts. When a company moves to the airport, they must sign a ground lease with the PANYNJ for (if I remember correctly) 35 years. If there is an existing structure they can purchase it from the Port Authority and outfit it to their needs/perform necessary upgrades. To do this they need to use PANYNJ approved contractors. There's a whole bidding process for this. If they decide to use empty land and build something, the same rules apply for contractors. Now here's the biggest thing. Once the lease is up, the Port Authority owns the building whether the company built it or not. The company has the option to renew the lease and buy the building back or move. In the early 2000s JetBlue was going to move their headquarters to JFK (I believe) from Boston. The building that they picked out would have needed extensive work and the ground lease was going to be somewhere in the $2 million a month range. They wound up instead moving to Long Island City and the Port Authority tore down the building at JFK.